This document discusses proteases and their role in wound diagnostics and healing. It begins with an overview of proteases and their functions in normal wound healing. Elevated or prolonged protease activity can impair healing by damaging new tissue formation. While protease activity is important in healing, too much can prevent wounds from progressing. Current methods for assessing protease activity include laboratory analysis of wound fluid and clinical assessment, but clinical signs alone do not always predict high protease levels. The development of an easy-to-use point-of-care protease test could help clinicians determine when wounds may have healing problems earlier and guide treatment.

1. THE ROLE OF PROTEASES IN
WOUND DIAGNOSTICS
an expert working group review
INTERNATIONAL
CONSENSUS

2. Editor:
Suzie Calne
PUBLISHER:
Kathy Day
MANAGING Editor:
Jason Beckford-Ball
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© Wounds International 2011
Supported by an unrestricted
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The views expressed are those
of the authors and do not
necessarily reflect those of
Systagenix.
How to cite this document:
International consensus. The
role of proteases in wound
diagnostics. An expert working
group review. London: Wounds
International, 2011.
FOREWORD
An international group of experts met in Cape Town, South Africa in February 2011 to build
on the 2008 World Union of Wound Healing Societies (WUWHS) consensus document
Diagnostics and Wounds1. The goal was to explore the importance of protease activity in wound
healing, and to gain consensus on the value of having an easy to use, point-of-care protease
test in clinical practice.
The key to success for such a test will be for clinicians to know clearly when, how and why to
use such a test. The expert consensus opinion of the meeting participants reaffirmed increased
protease activity as currently the best available marker for impaired wound healing when other
causes have been excluded, and that effective use of a protease test kit at the point of care has
the potential to change wound care globally.
Professor Keith Harding
Expert working group
Keith Harding, School of Medicine, Cardiff University (UK)
David G Armstrong, Southern Arizona Limb Salvage Alliance (SALSA), University of
Arizona (USA)
Simon Barrett, Humber NHS Foundation Trust (UK)
Hanna Kaufman, Wound Healing Unit, Maccabi Healthcare Services, Haifa (Israel)
Jose Luis Lázaro-Martínez, Diabetic Foot Unit, Universidad Complutense, Madrid (Spain)
Dieter Mayer, Clinic for Cardiovascular Surgery, University Hospital of Zurich
(Switzerland)
Zena Moore, Royal College of Surgeons in Ireland, Dublin (Ireland)
Marco Romanelli, Wound Healing Unit, University of Pisa (Italy)
Douglas Queen, Department of Dermatology & Wound Healing, Cardiff University (UK)
Greg Schultz, University of Florida, Gainesville, Florida (USA)
Thomas Serena, Pennsylvania North Centers for Advanced Wound Care, Pennsylvania (USA)
Gary Sibbald, University of Toronto (Canada)
Robert Snyder, Wound Healing Center, University Hospital, Florida (USA)
Robert Strohal, Federal University Teaching Hospital of Feldkirch (Austria)
Kathryn Vowden, University of Bradford and Bradford Teaching Hospitals NHS Foundation
Trust (UK)
Peter Vowden, University of Bradford and Bradford Teaching Hospitals NHS Foundation
Trust (UK)
Paolo Zamboni, University of Ferrara (Italy)
•

3. What are proteases?
THE ROLE OF PROTEASES IN WOUND DIAGNOSTICS
What are proteases?
Proteases are enzymes
that break down proteins
into peptides and
amino acids. In wound
healing, the major
proteases are the matrix
metalloproteinases
(MMPs) and the serine
proteases, eg elastase.
In general, different
wound-related proteases
act on different
proteins. These include
extracellular matrix
(ECM) and connective
tissue proteins
such as collagen,
gelatin, proteoglycans
and elastin.
Proteases (also known as proteinases) play key roles in the normal wound healing process2
(Table 1). Proteases are enzymes that act on proteins by breaking them down into peptides and
amino acids. In wound healing, the major proteases are the matrix metalloproteinases (MMPs)
and the serine proteases, eg elastase. In general, different wound-related proteases act on
different proteins. These include extracellular matrix (ECM) and connective tissue proteins such
as collagen, gelatin, proteoglycans and elastin.
In the normal wound healing process, proteases break down damaged ECM proteins and
foreign material so that new tissue can form and wound closure can occur in an orderly
fashion. However, when the level of protease activity is too high the delicate balance between
tissue breakdown and repair is disturbed.
Excessive wound proteases lead to the degradation of newly formed ECM and other proteins,
eg growth factors and receptors. As a result wound healing is impaired due to ECM damage
and abnormal prolongation of the inflammatory stage of healing that prevents the wound from
progressing to the proliferative phase2.
Protease activity is an essential part of wound healing3. However, once out of control, and if left
unchecked, proteases in wounds may cause sufficient damage to the extracellular matrix, growth
factors and receptors to impair healing and destroy normal tissue
SOURCES OF PROTEASES
As well as being secreted by the cells involved in the repair process, eg fibroblasts and
endothelial cells, proteases are produced by immune cells stimulated by an inflammatory process
or infection. For example, human neutrophil elastase (HNE) is produced by neutrophils and is
responsible for fibronectin degradation in non-healing wounds.
This is important because fibronectin degradation products stimulate the further release of
MMPs4,5. Intact fibronectin (which is necessary for cell adhesion and growth factor signalling)
is absent in non-healing wounds, but has been shown to reappear in the wound bed as healing
begins6.
Elevated tissue iron levels in chronic venous disease due to extravasation of red blood cells has
been suggested to be another stimulus to over-expression of MMPs7. In addition, patients with
chronic venous disease who also have a haemochromatosis gene mutation (C282Y) that causes
abnormal iron metabolism have significantly increased risk of developing a venous leg ulcer8.
In the future, testing for genetic variants may become part of the screening process for assessing
risk of ulceration and probability of healing.
•
Table 1 | Main roles of proteases in normal wound healing2
Main phase of healing Role of proteases
n Inflammation n Removal of damaged ECM (aids autolytic
debridement)
n Proliferation n Degradation of capillary basement membrane
for angiogenesis
n Aiding detachment and migration of cells
n Remodelling n Contraction of scar ECM
n Remodelling of scar ECM

4. Another source of proteases in wounds is bacteria. In addition to stimulating protease production
via activation of the immune system, some bacteria in wounds may themselves secrete
proteases. However, the impact of bacterially derived proteases on wound healing and their
contribution to total wound protease activity remains to be determined.
More is currently known about proteases than any other biochemical marker involved in
wound healing
ELEVATED PROTEASE ACTIVITY AS A MARKER FOR NON-HEALING
There is a large body of evidence from animal and human studies suggesting that protease
activities (the MMPs and human neutrophil elastase [HNE] in particular) are elevated in wounds
that fail to progress towards healing9-20.
In the normal course of wound healing, there is a rapid initial increase in protease levels21,22. The
levels peak at about day three and start to reduce by about day five (Figure 1). In non-healing
wounds, however, not only do proteases reach higher levels than in healing wounds, but they
persist far longer. The result is a highly destructive wound environment.
Although the relationship between proteases, inflammation and wound healing is broadly
understood, there are other markers associated with inflammation (such as TNF-alpha) that may
warrant further investigation as potential candidates for diagnostic tests23. However, data to date
suggest that proteases may be the most promising biomarker for assessing wound healing at a
biochemical level.
•
The reasons for the imbalance between increased protease production and a lack of protease
inhibition in non-healing or chronic wounds is not fully understood, but regular monitoring of
protease activities during treatment may help to guide appropriate management •
Figure 1 | Changes in
protease activity in wounds
3 | INTERNATIONAL CONSENSUS
Normal
wound healing
Non-healing
wound
Time
Inflammatory protease activity

5. Understanding the role of proteases
When educating clinicians about proteases, it is important to teach the concept of balance
and imbalance in healing, ie the balance between synthesis and degradation of ECM. The main
learning points are:
■■ Proteases are important for organising and remodelling new ECM. There is a burst of protease
activity at the start of acute wound healing. In normally healing wounds, the activity peaks in
the first couple of days and then declines to very low levels by one week21
■■ Stimuli that may prolong high protease activity include the presence of damaged tissue,
THE ROLE OF PROTEASES IN WOUND DIAGNOSTICS
foreign material, bacteria and biofilms
■■ If protease activities are too high they start degrading and destroying the ECM and damage
newly formed tissue, harm the wound bed and delay healing
■■ Interventions that reduce harmful proteases and correct the imbalance may aid healing24.
PREDICTING HEALING PROBLEMS
Wounds that are difficult to heal are often labelled as 'chronic'. However, this may not be helpful because
the term 'chronic' implies long duration and the need to wait to see if a wound is slow to heal. Clinicians
know that wounds in patients with certain comorbidities, eg diabetes mellitus, or in patients on certain
medications, eg steroids, can be identified from the time they occur as being difficult to heal.
Furthermore, the term 'chronic' may exclude acute wounds, eg surgical wounds, which have
healing problems. As a result a number of terms are used to describe wounds that may be slow
or difficult to heal (see Box 1, left).
There are numerous factors other than duration that influence ability to heal. Initial assessment
of all wounds should include assessment for these factors (Table 2). The regimen of care for
patients with a wound of any type should, therefore, include management of any correctable
factors. Early recognition of correctable factors provides clinicians with the opportunity to
implement care that can speed healing.
Equally important, however, is that clinicians recognise when a wound is unlikely ever to heal,
eg in patients with malignancy or advanced disease, on chemotherapy or on high dose steroids.
Box 1: Terminology of
wounds with healing
problems (adapted
from25)
●● Chronic
●● Delayed
●● Hard to heal
●● Stalled
●● Recalcitrant
●● Difficult
●● Complex
●● Fail to respond
For further discussion on
non-healing wounds, go to
the Chronic Wound Debate
in the Wounds International
Journal, Vol 1; Issue 2 (www.
woundsinternational.com)
• POINTS FOR PRACTICE
The importance of protease activity
n High protease activity is the best available biochemical marker for predicting poor wound healing of
both acute and chronic wounds
n If wound protease activity and ratios are appropriate for the stage of wound healing, healing will be
more orderly and timely
n Research is required to identify and clarify:
- what level of protease activities are appropriate during autolytic debridement
- why and at what specific point on the healing trajectory protease activity may become imbalanced
- the protease activity typical of stalled and healing wounds for different wound types, eg pressure
ulcers, vasculitic wounds
- how patient factors such as age, hormone levels and co-morbidities affect protease activity
- the synergistic and chronological relationships between different proteases, ie how the different
MMPs and elastases work together to degrade ECM proteins
- the impact of bacterial contributions to protease activities
n Establishment of a registry that collects data on protease activities in different wound types at different
stages of healing would provide useful data on wound healing prognosis

6. REDUCTION IN WOUND AREA AS A PREDICTOR OF HEALING
Research has suggested that a reduction in wound area by weeks two to four is a good predictor
of ability to heal by week 12. For venous leg ulcers, a 20–40% reduction in wound area within
two to four weeks has been found to be predictive of healing27, whereas for diabetic foot ulcers, a
reduction of >50% by week four is predictive of healing28–30.
It is logical, therefore, that wounds that do not show these levels of healing within these time
frames trigger the need for reassessment and re-evaluation of the care regimen.
However, rather than waiting until problems develop, it would clearly be very beneficial to be
able to identify even earlier when advanced interventions may assist with healing. Testing for
markers of healing, such as protease activity, may help clinicians predict which wounds will have
problems2.
Even when wound and patient care is optimal and infection has been excluded, some wounds
do not heal. These wounds may have persistent inflammation with high protease activity that
is preventing progression to the proliferative stage of healing •
Table 2 | Factors that may influence wound healing ability26
Area Factors
n Patient n Aetiology
5| INTERNATIONAL CONSENSUS
n Comorbidity, eg diabetes mellitus, autoimmune disease
n Allergy
n Medication, eg steroids
n Psychosocial status
n Pain
n Concordance
n Wound n Duration
n Size
n Wound bed condition
n Ischaemia
n Inflammation/infection
n Anatomical site
n Treatment response
n Care provision n Skill and knowledge of clinicians
n Healthcare system (availability, cost/reimbursement)

7. Assessing protease activity
CURRENT METHODS FOR ASSESSING PROTEASE ACTIVITY
Laboratory analysis
Currently, it is very difficult to assess the level of proteases in wounds. Research studies have
analysed types, levels and activities of proteases in wound fluid derived from biopsies obtained
in laboratory conditions. These studies have involved several different techniques, eg gelatin
zymography that primarily detects MMP-2 and MMP-9, ELISAs that use antibodies to measure
levels of proteases, and assays that measure the enzymatic activity of proteases.
The results of these studies show a consistent trend of low levels of protease activity in acute
healing wounds, and high levels in stalled or poorly healing wounds that decrease when the
wounds begin to heal10,17. However, for most clinicians, laboratory evaluation of protease activity
is not feasible.
Clinical assessment
In wounds that are not healing as expected, excess protease activity may be suspected in
a wound that has not responded to treatment or that has stalled after initially successful
treatment if:
■■ comprehensive treatment has included correction of the underlying cause (eg compression
for venous stasis), management of patient concerns (eg pain) and optimal local wound care
(debridement and provision of a moist wound environment), and;
■■ infection is not suspected or has been ruled out.
Clinical signs of inflammation, which may be indicative of high protease activity may be difficult
to distinguish from those of infection. Signs may include a red wound bed, absent or diminished
granulation that may bleed easily on contact, and increased exudate and pain levels.
However, although the majority of uninfected non-healing wounds will have excess proteases, a
percentage of non-healing wounds will not have excess proteases.
Consequently, clinicians may wrongly assume that a chronically inflamed uninfected non-healing
wound, which has received appropriate care and management of underlying causes, has high
protease activity.
An on-going study of over 100 acute and chronic wounds has shown that skilled clinicians using
the clinical criteria for chronic inflammation have not been able to accurately predict which wounds
have high protease activity. In fact, the only wounds in which protease activity has correlated with
clinical examination are vasculitic ulcerations31. Figure 2 (overleaf) demonstrates the difficulty of
predicting high protease activity based on clinical examination alone.
Clinical signs do not always predict the presence of high protease activity. Accurate detection
of elevated protease activity would aid in the appropriate use of treatments aimed at modifying
protease activity and would help to avoid inappropriate use of advanced wound care products
Relevance of protease levels to healing
Studies show a consistent trend of low levels of protease activity in acute healing wounds, and high levels
in stalled or poorly healing wounds that decrease when the wounds begin to heal10,17. However, for most
clinicians, laboratory evaluation of protease activity is not feasible and clinical assessment is necessary.
THE ROLE OF PROTEASES IN WOUND DIAGNOSTICS
•

8. A: A 52-year-old non-diabetic male
with a long-standing venous leg
ulcer. There is minimal exudate
after treatment with a topical
silver agent. Recently treatment
has been changed to a collagenase
and compression wrapping. He has
minimal pain.
Answers
Positive test for elevated protease activity: A, D, E
Negative test for elevated protease activity: B (both legs), C, F
Figure 2 | Clinical
observation cannot detect
high protease activity. Do
these pictures show wounds
with high or low protease
activity? (See answers at the
bottom of the page — photos
courtesy of Tom Serena)
7 | INTERNATIONAL CONSENSUS
B: A 40-year-old non-diabetic
woman with bilateral lateral gaiter
chronic venous leg ulcers currently
being treated with topical alginate
and compression. The right leg
ulcer (above left) has a clean
granulating base. The left leg ulcer
has repeatedly developed tan slough
requiring curettage.
C: Stage III pressure ulcer treated
with ORC-silver/collagen.
D: A non-diabetic patient with
an acute wound on the dorsum of
her hand after an intravenous line
infiltrated. The wound is healing.
E: A patient with known vasculitis of
the lower extremity.
F: Diabetic plantar neuropathic ulcer
treated with topical silver alginate
and hyperbaric oxygen.

9. Wounds that are not healing despite correction of underlying causes, exclusion of infection
and optimal wound care may be stuck in a persistent inflammatory state with high
protease activity. Treatment of such wounds requires a systematic, often interdisciplinary
approach that focuses on correcting the underlying cause of inflammation. Care should
be provided in keeping with appropriate local protocols that use the basic tenets of good
wound management.
The use of a point-of-care diagnostic test for protease activity may assist the clinician in the use
of advanced therapies by indicating clearly which treatments are and are not appropriate, and
when to start and stop treatment
Principles
There are a number of interventions that may reduce protease activity in a wound. The three
key principles involved in treating wounds with suspected excessive protease activity are:
■■ treat the underlying cause and any factors that may aggravate the wound, eg compression,
pressure relief, correct ischaemia and suboptimal nutrition
■■ optimise the wound bed and patient condition, eg wound bed preparation (including
debridement), negative pressure wound therapy (NPWT), modulate bacterial load
■■ modulate protease activity, eg protease-modulating dressings.
Caution should be exercised when using skin/dermal equivalents in complex non-healing
wounds where protease activity is high because degradation of the matrix is likely to occur
REDUCING EXCESS PROTEASE ACTIVITY
The following techniques may reduce protease activity in wounds:
■■ Cleansing: regular wound cleansing may help to reduce protease activity by removing surface
debris that could act as an inflammatory stimulus. Cleansing may also help to reduce protease
activity by removing protease-containing wound fluid. Studies that examine the effects of
cleansing on protease activity are awaited
■■ Debridement: removal of slough at every dressing change, or surgical or sharp
debridement at appropriate intervals, may help to reduce excessive protease activity by
removing necrotic tissue and reducing bacterial load that may be acting as inflammatory
stimuli. Again, studies that examine the effect of debridement on protease activity
are awaited
■■ Protease inactivators: protease-modulating dressings (eg collagen/oxidised regenerated
cellulose [ORC]) that bind to and inactivate proteases (MMPs and elastase)32,33
■■ Antiseptic dressings (eg iodine or silver): a reduction in bacterial levels may reduce protease activity
by reducing host and bacterial protease production34. It has been postulated that silver may also
reduce MMP activity by displacing the zinc ion necessary for MMPs to function from the enzymes35
■■ Anti-inflammatories: oral or topical doxycycline is a potent anti-inflammatory and
antimicrobial that inhibits protease activity36 — steroid therapy has an anti-inflammatory
effect by upregulating the expression of anti-inflammatory proteins and downregulating the
expression of pro-inflammatory proteins. Experience of these treatments to date is mainly
in vasculitic wounds and pyoderma gangrenosum. Studies in other wound types and the
possible use of these treatments in combination are awaited
■■Dressings and devices that absorb/remove wound exudate: absorbent dressings and materials
may reduce protease activity by removing protease-containing wound fluid37, although this has
yet to be demonstrated in a clinical context. An effect of NPWT in stimulating healing may be to
reduce protease activity38,39.
THE ROLE OF PROTEASES IN WOUND DIAGNOSTICS
•
Management of high protease activity
•

10. When using advanced therapies such as protease-modulating dressings or infection control
products, a point-of-care test to measure changes in protease activity may be useful in monitoring
the effectiveness of treatment and indicating whether there is a need to modify therapy
PROTEASE-MODULATING DRESSINGS
As with all advanced wound care products, the use of protease-modulating dressings should be
carefully integrated into the overall care plan, which needs to be appropriate to the condition of the
wound bed, bacterial load and exudate level.
In general, protease-modulating dressings, eg ORC/collagen, are used for short courses of two
to four weeks, followed by a full reassessment of the effectiveness of treatment. Intermittent or
pulsed treatment is also sometimes used, eg two weeks of treatment with the protease-modulating
dressing followed by two weeks without the dressing.
A collagen/ORC dressing has been shown to reduce protease activity and to have a positive effect
on healing in a variety of non-healing wounds24,33,40.
The use of a protease-modulating dressing should be a clearly timed intervention, ie the proposed
duration of treatment should be clearly documented with a review date. It is essential that regular
assessments of healing progress, eg of wound margin, base and wound area, are conducted during
treatment. For venous leg ulcers, a guide for improvement indicating that healing is likely would be
a 20–40% reduction in wound area at four weeks27.
The introduction of a point-of-care test for excessive protease activity would allow more targeted
use of protease modulators to reduce excessive protease activity. A protease activity test may also
provide an opportunity to examine other potentially beneficial effects of continued use of protease
modulators on healing once proteases are under control.
Current knowledge of the role of proteases in delayed healing suggests that every stalled or
slow to heal uninfected wound in a patient that has been adequately assessed and managed is a
potential candidate for a point-of-care test for protease activity
•
•
9 | INTERNATIONAL CONSENSUS

11. The role of a point-of-care
protease test
Ideally, a new diagnostic tool for use in wounds will indicate specific modifications to practice
or treatment that will move the wound towards healing1.
A point-of-care protease test will be an innovation in wound care. It is anticipated that it
will be used to detect whether protease activity is elevated in wounds that are not healing
as expected.
USING A PROTEASE TEST
A point-of-care protease test may help clinicians to make informed, cost-effective decisions
about which treatment is or is not appropriate. For example, it would not be appropriate
to use a protease-modulating dressing in a wound with low protease activity, and tissue-engineered
products, scaffolds and skin grafts would be inappropriate in a wound with
THE ROLE OF PROTEASES IN WOUND DIAGNOSTICS
elevated protease activity.
Advantages of guiding therapy in this way may include less frequent dressing changes,
avoidance of unnecessary interventions, reduced nursing time, fewer clinic visits, shorter
overall treatment duration, earlier recognition and prevention of complications, improved
quality of life, faster healing and earlier return to work. These potential benefits may lead
regulators in the future to require the test before the use of specific treatments.
Monitoring proteases, eg through weekly testing, may allow clinicians to recognise whether
care is effective in reducing protease activity and, therefore, whether the current treatment
approach is appropriate. It has been speculated that the results of a point-of-care protease
test may eventually be used to identify successful treatment and may become an alternative
outcome measure to healing.
Point-of-care protease testing may be shown to have the potential to aid early identification
of wounds that may be potentially hard to heal, thus avoiding the delays and associated risks
caused by 'waiting long enough' before classifying a wound as hard to heal. This may also help
to avoid more expensive diagnostic tests, eg invasive tests such as wound biopsy, and could be
used to help confirm the diagnosis of inflammatory conditions, eg vasculitis.
An easy-to-use point-of-care protease test may present an opportunity for remote management of
wounds, ie clinicians/patients may be able to test for high protease activity in a wound and then gain
advice or make decisions about referral based on the results. For example, a less experienced clinician
could use the test as a signal to refer to specialist or not, dependent on the result of the test.
To gain acceptance of a point-of-care protease test, payers will need evidence of cost-effectiveness,
there will need to be widespread adoption by key opinion leaders, and clear
evidence of benefits.
For a point-of-care test to become integral to practice, data will be required that demonstrate
the validity of the test in a spectrum of wound types in clinical practice. A key unanswered
question is how to deal with wounds with high proteases that go on to heal without
complication and those with low proteases that fail to heal •

12. Potential pathway for the use of a
point-of-care protease test
The use of a point-of-care protease test in wounds that fail to respond must be in the context of
continued re-evaluation and optimisation of care in accordance with local wound care practices and
policy. Figure 3 and Table 3 illustrate how such a test might be used in practice once introduced.
Further research will be required to fully characterise the role of a point-of-care protease test in
clinical practice
•
Figure 3 | Potential pathway
for use of a point-of-care
protease test
Reassess the patient
and the wound
Re-evaluate and
modify treatment as
necessary
11 | INTERNATIONAL CONSENSUS
Is the wound not responding
to standard care or has it stalled
after an initial response*?
Yes
Has the wound been accurately
diagnosed, assessed and
appropriately treated?
Yes
Has infection been treated or
excluded?
Yes
Point-of-care test for elevated
protease levels
Are protease levels elevated?
Yes
Topical/systemic management
of protease levels (see page 8)
Review after 2-4 weeks
Is satisfactory healing
progress being made?
Yes
Exclude or treat
infection
Is satisfactory
healing progress
being made?
No
Retest using point-of-care
test for elevated
protease levels:
• If protease levels
have decreased,
conduct a complete
review of patient
and wound history
and treatment
regimen
• If protease levels
remain high,
reassess the
patient, especially
for infection and
adjust the regimen
as necessary
(see Table 3 on
next page)
Retest using point-of-care
test for elevated
protease levels:
• If protease levels
have decreased,
consider whether
continuation
of treatment
is justified, eg
if benefits are
likely to outweigh
disadvantages
• If protease levels
remain high,
continue protease-modulating
therapy
and reassess,
especially for
infection (see Table
3 on next page)
Continue with
current regimen
with regular review
No
Reassess
No
No
Yes
No
No
Reassess Reassess
*∗Identify healing status through early comprehensive assessment that includes examining and correcting the cause of the wound. Healing
problems are more likely to occur in patients who are compromised or who have co-morbidities such as diabetes or malignancy.

13. Payers are likely to embrace the availability of an objective measure to guide treatment if it
allows clinicians to treat early and for a shorter duration to achieve healing and that testing can
be shown to reduce costs overall •
THE ROLE OF PROTEASES IN WOUND DIAGNOSTICS
SIGNS/SYMPTOMS OF
INFECTION
PROTEASE ACTIVITY
Low protease Elevated protease activity
activity
LOW BACTERIA No signs of infection Moisture balance
dressing
Protease-modulating
dressing
HIGH BACTERIA
Superficial infection
Three of:
●● Non-healing
●● Exudate
●● Pain
●● Red friable wound
●● Debris, smell
Antimicrobial dressing Protease-modulating
dressing with antimicrobial
activity; +/- systemic
antibiotic
Deep/systemic infection:
Three of:
●● Size
●● Temperature
●● Pain
●● Fistulae/bone exposed
●● New/satellite wounds
●● Erythema/oedema
●● Smell
●● Elevated acute phase
proteins
Systemic antibiotics Systemic antibiotic
Systemic anti-inflammatory
Antimicrobial dressing
Protease-modulating
dressing with antimicrobial
activity
Table 3 | Relationship
between protease activity,
bacteria/infection, and
treatment modality
• POINTS FOR PRACTICE
Using a point-of-care protease test
n Only use a point-of-care protease test if the results will influence clinical decisions on topical wound care
n Avoid user-induced false positives and false negatives by carefully following the instructions
n Know how a positive result and a negative result are shown by the test
n Understand what these results mean and what implications they have for care
n Know whether to test before or after debridement or cleansing
n If cleansing should take place before testing, know which solution(s) may be used, and how the
solution used may affect test results
n Know what type of wound fluid to use for the test and how much is needed
n Know how to collect the wound fluid
n Know how soon after collection of the wound fluid the test needs to be done
n Know whether and how the presence of blood or necrotic tissue may affect the test results
n Know what to do if wound fluid is difficult to access or is not present
n Know why, when and how often to retest
n Understand the validity of the test in different wound types, ie how accurately the test measures
protease activity in different wound types
n Understand the sensitivity and specificity of the test and how these may affect test interpretation,
ie how often true positives (reported high protease activity when activity is high) and true negatives
(reported low protease activity when activity is low) are indicated by the test

14. References
1. World Union of Wound Healing Societies (WUWHS). Principles of best
practice: Diagnostics and wounds. A consensus document. London: MEP
Ltd, 2008.
2. Gibson D, Cullen B, Legerstee R, et al. MMPs Made Easy.
Wounds International 2009; 1(1): Available from http://www.
woundsinternational.com
3. Agren MS, Mirastschijski U, Karlsmark T, Saarialho-Kere UK. Topical
synthetic inhibitor of matrix metalloproteinases delays epidermal
regeneration of human wounds. Exp Dermatol 2001; 10(5): 337-48.
4. Grinnell F, Zhu M. Fibronectin degradation in chronic wounds
depends on relative levels of elastase, a1 proteinase inhibitor and a2
macroglobulin. J Invest Dermatol 1996; 106: 335-41.
5. Grinnell F, Zhu M. Identification of neutrophil elastase as the
proteinase in burn wound fluid responsible for the degradation of
fibronectin. J Invest Dermatol 1994; 103(2): 155-61.
6. Herrick SE, Sloan P, McGurk M, et al. Sequential changes in histologic
pattern and extracellular matrix deposition during the healing of
chronic venous ulcers. Am J Pathol 1992; 141(5): 1085-95.
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